1. Field of the Invention
The invention relates to a suction device, in particular a suction box or a suction roll, for a machine that manufactures or processes a fibrous pulp web, such as a paper web.
2. Discussion of Background Information
A suction device, in particular a suction device for a suction box or a suction roll, that extends in a direction transverse to the web run direction in a machine for manufacturing a fibrous pulp web is known, for example, from DE 44 40 948. The suction device disclosed in DE 44 40 948 is designed as a suction roll, with a roll sleeve that is mounted on a pivot, that is perforated, and that has a vacuum connection to create a vacuum in the roll interior. The vacuum region of this suction zone expands to the roll perforations. The suction zone extends transversely over the width of the web, along the longitudinal axis of the suction roll. A displaceable partition wall is designed in the interior of the roll, along the longitudinal axis of the roll, which allows the division of the suction zone into a suctioned section and a section that is not suctioned.
Such a suction roll is used, for example, in a paper manufacturing machine where a moist paper web must be transferred from one machine section (e.g. a press section) to the subsequent machine section (e.g. a drying section). When feeding the web into the paper machine, initially only a narrow peripheral strip of the web runs over the suction roll. Accordingly, only a small portion of the suction zone is connected to the vacuum source. Thereafter, as one gradually feeds the web into the machine and the strip widens (up to the full width of the web in the end), the width of the suction zone is correspondingly extended through movement of the displaceable partition wall. By expanding the suction zone in coordination with the increasing width of the web being fed into the processing machine, the suctioning of air through perforations that have not yet been covered by the paper web can be avoided. Otherwise, a markedly greater amount of energy would be required to create the vacuum in the suction zone.
A disadvantage of such a known construction is that contaminant can be deposited on the displaceable partition wall, and under certain conditions this may result in machine malfunctions. It is also possible that wear can lead to leakage losses. With very wide paper machines (such as 10 m in width, for example) it is also difficult to dependably design the mechanism, including the driving mechanism, for the displaceable partition wall.